A prototype of an advanced system for measuring spatial distributions of radiation doses will be developed for application in dose planning for radiotherapy. It will utilize special large- area arrays of small, thin-layer thermoluminescent phosphor spots on thin substrate films that can be placed between the transverse slices of human radiological phantoms and subsequently evaluated in an automated laser-heated thermoluminescence dosimetry (TLD) reader specially designed for these applications. The dosimeter arrays will be fabricated by screen printing mixtures of fine-grain TLD phosphor powder and a two-component high temperature silicone binder onto aluminized films. In the TLD reader phosphor spot is sequentially heated with the beam from a closed-loop controlled, RF-excited cw CO2 laser, Special optics will provide a laser heating beam of uniform square intensity profile which assures heating of each dosimeter spot without spatial temperature variations. Software and electronics will be developed for automated dosimeter handling, control of all laser functions (including the possibility of selected time-varying special laser heating cycles), thermoluminescence emission detection, and automated iso-dose curve plotting. Dosimeter arrays of 12x12 in 2 area, spot sizes between 1x1 mm2 and 4x4 mm2, spot layer thicknesses ranging from 4 mg/cm2 to 15 mg/cm2, and spot separations (center to center) down to two millimeter will be provided. Commercially available thermoluminescence phosphors will be utilized.